The present invention relates to a shielding device, and particularly to a shielding device for providing EMI (electromagnetic interference) protection for electronic components on a circuit board.
Related inventions are disclosed in U.S. Pat. Nos. 5,400,949, 5,365,410 and 5,742,488. Generally, EMI shielding devices take the form of metal or metallised plastic covers designed to be placed over electronic components on a circuit board. To prevent the shielding devices from separating from the circuit board, the most common method of attaching the shields to the circuit board is by a soldering process. However, the process of de-soldering the shielding device from the circuit board to repair the electronic components beneath is very difficult.
Many detachable shielding devices are provided to solve this problem. Related inventions are disclosed in U.S. Pat. Nos. 5,252,782, 5,353,201, 5,419,722, 5,434,747, 5,436,399, 5,495,399, 5,660,558, 5,742,004, 5,014,160, 5,198,618 and 5,895,884.
Referring to FIG. 1, a conventional shielding device 5 comprises a cover 51 and a base frame 50. A plurality of flanges 511 depends from outer edges of the cover 51. The base frame 50 comprises side walls 500 and a plurality of apertures 501 defined in the side walls 500. Each flange 511 comprises an inwardly projecting dome shaped projection 512 for engaging with the apertures 501 when the shielding device 5 is in closed position. The press dies used to form the punched apertures 501 have a short life, which increases the cost of the shielding device 5. Furthermore, after assembly the dome shaped projections 512 lock too firmly with the corresponding apertures 501. Therefore, it is difficult to detach the cover 51 from the base frame 50. Finally, it is sometimes troublesome to precisely align the projections 512 with the apertures 501, resulting in an inconvenient assembly of the shielding device 5.
Thus there is a need for an improved shielding device which can overcome the disadvantage of the prior art.
A main object of the present invention is to provide a shielding device for providing EMI (electromagnetic interference) shielding for electronic components on a circuit board.
Another object of the present invention is to provide a shielding device which is easily assembled/disassembled and which has a low manufacturing cost.
To fulfill the above-mentioned objects, according to a preferred embodiment of the present invention, a shielding device comprises a top cover and a frame. The top cover comprises a body portion with a plurality of holes being formed in the body portion. A plurality of flanges extends downward from outer edges of the body portion. A dome shaped projection is formed in a central portion of each flange. The frame comprises a narrow top wall and a side wall. An engaging portion in the form of an elongated groove depressed inwardly is formed in the side wall for detachably engaging with corresponding dome shaped projections. The top wall extends inwardly and horizontally from the top edge of the side wall. The side wall continues downwardly from the engaging portion for mounting on the circuit board. The engaging portion is formed with a concave outer surface for receiving corresponding projections of the top cover.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.